In the basic studies of this proposal, we will investigate both bioacoustic phenomena in the ear canal and electrophysiological responses of single cochlear nerve fibers in the same animals under two-tone,. tone-pip, click and no acoustic stimulation with and without electric stimulation of the crossed olivocochlear bundle, so that biomechanical transduction processes of the cochlea can be closely related to bioacoustic phenomena detectible in the ear canal. Similarly, we will investigate two-tone distortion products acoustically measured (in the ear-canal) and psychoacoustically measured in the same normal human subjects. Further, we will characterize species differences in bioacoustic properties looking into the ear canal for normal humans, monkeys, chinchillas and cats. In the clinically-oriented studies of this proposal, we will measure the norm and the variability of various ear-canal bioacoustic measures that reflect cochlear biomechanical activity for humans, monkeys, and chinchillas with normal or damaged organ of Corgi in order to develop a new noninvasive, objective and reliable method of diagnosing human cochlear disorders. In order to validate the ear-canal bioacoustic tests, the functional state of the ears will be assessed by standard audiological test battery for human subjects' ears and assessed by the compound-action-potential electrocochleogram and the histological cytocochleogram for animal subjects' ears. These bioacoustical, meurobiological and psychoacoustical results from humans and animals with normal and pathological cochlea should be helpful in improving the knowledge of basic mechanisms underlying the remarkable performance of the ear as well as in developing clinically useful diagnostic methods.